In the case of a new aquarium, what is being described here is the phenomenon of “New Tank Syndrome”. It is quite common and not particularly dangerous, but it is certainly unsightly. Just like most other living organisms, the bacterial cloud consumes oxygen, so it is not a bad idea to elevate the oxygen content to ensure any fish are not oxygen deprived during this problem. If they seem to be gasping, add an airstone to agitate the surface.

New aquariums start with sterile water, the municipal water supply is often treated with antibiotic compounds to kill any pathogenic organisms that might affect a human drinking it. In effect they make the water “potable”. Potable water is deadly to bacteria, but it is also deadly to fish as well. In most cases the munipal water company uses compounds such as chlorine (in most cases) and chlorine when the water needs to be transported a great distance. Although the two compounds require different doses of the same compound, once they are removed, the water is left with no living organisms alive, but the ability to support them should they arrive. The first ones to arrive are bacteria that occupy the water column. These are very rapid replicating bacteria that split in two on a reguular basis. This progression is termed geometric replication, one becomes two, two become four, four double to eight and so on. Each generation roughly doubles in size. Since the water is sterile, there are few predators or other dangers to this uncontrolled explosion at the lowest living level.

The only limiting factor to this unchecked population growth is the amount of food available. In many cases the water from the tap has much more in it than just water and chlorine, it has plenty of dissolved organic material as well. This is the food that the bacteria require and assuming there is enough of it available the bacterial population rises higher and higher. In a new aquarium it takes about three days for the heterotrophic bacterial density to get so packed that the bacterial bloom can be seen by the naked eye. It appears, as mentioned, almost as if someone had poured a glass of milk into the aquarium. Depending on the amount of dissolved organics available for the bacteria to use, this can become quite dense and very cloudy. The unchecked growth of the bacteria in the water is termed a bacterial bloom.

As mentioned, this is a common problem for many new aquariiums where the water that has been added carried with it considerable amounts of dissolved nutrients for the bacteria to grow. It is also the limiting factor, when the food finally runs out under the weight of biomass of geometric replication, the bacteria will die of starvation. Depending on the situation in the aquarium, that might take quite a while if too much added food is available on an ongoing basis – the used foods can be replaced by the feeding regime of the aquarist and the the problem becomes perpetual.

The “New Tank Syndrome” will occur with or without fish. The bacterial cells are much too small to be captured by any ordinary filter, so this is not the fault of choosing a bad filter. If the tank clouds before you add fish, simply do nothing. The cloud will dissipate on its own as the fight for survival at the bacterial level, one of the most fiercely aggressive levels of living organisms, occurs with each individual requiring food to survive.

Cloudy water can occur much later in the aquarium’s life cycle. Here it is most like from overfeeding or excess organic materials accumulating in the aquarium. Once again this is a case where the dissolved organics in the water column rise to a level where they are no longer a limiting factor, and the bacteria bloom out of control. The most basic cure is to reduce the amount of organic material wastes in the aquarium. Since the aquarist is ultimately responsible for what is entering the aquarium, the cure is to reduce the input. Always examine the aquarium for dead fish or decaying material, perform a proper water change and use the exiting water to drive a gravel cleaner through the substrate to ensure the worst debris is being removed from the aquarium.

Once the aquarium is back into better hygienic shape, stop feedng the aquarium for at least three days. Chances are the original cause was overfeeding, and this forces the fish to go looking for a meal rather than being handed one at the surface. The fish will look harder if they are hungry and they will help clean the tank a bit. As the three days pass, the bacteria will begin to remove the organic overload as the population continues to expand and hopefully die back again to invisible.

This is not the filter’s fault, the bacteria are much too small to be trapped by the filter media in most cases. The only way to help the filter capture this small an organism is to make it clump together. There are clarifier products on the market that ionically force the bacteria to coagulate into large clumps that the fiter can trap. The problem here is that the result is a gooey mess that is quite difficult to clean away. Whenever you decide to use a floculant – a product that clumps all particles together, you should not use standard filter materials. The best to use if Poly Wool, Filter Floss or sometimes it is termed Angel Hair. This is a very fine threaded product that is quite cheap and is purchased to be disposed once it has been used. It will trap the clumps quite readily, and is easy to dispose. Don’t use expensive standard media or cartridges, you are only going to have to throw them away right after use.

One final word of warning, if you do decide to use a floculant, be very careful in your doses. This is one product where more is definitely not better. An overdose reverses the ionic effect and the water gets even more cloudy and difficult to clear. It is a one time thing, not something you can depend on often. Reducing the amount of food going into the aquarium and ensuring anything that dies is removed as fast as possible will help keep the tank clear and cloudless better than any medication or chemical treatment.

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